1. Field of the Invention
The present invention relates to a rotary laser emitting apparatus which emits laser light while rotating.
2. Description of the Related Art
For example, in surveying work in association with civil engineering work or the like, it is well known that a rotary laser emitting apparatus which emits laser light while rotating about a rotation axis and a receiver which receives the emitted laser light are used to measure a height and a slope angle of a light receiving position against a plane orthogonal to the rotation axis based on signals of the laser light received by the receiver. Such a rotary laser emitting apparatus usually has a structure such as a laser emitting section which is rotatably provided on a foundation and emits the laser light in a direction orthogonal to the rotation axis. In order to heighten the accuracy of the measurement, the rotary laser emitting apparatus is expected to control or suppress an occurrence of shake of the emitted laser light in relation to the rotation axis as much as possible.
As such a rotary laser emitting apparatus, a structure is proposed such that a rotary body is provided rotatably about a rotation axis on a foundation; two or more pentaprisms stacked up on the rotation axis are contained in the rotary body; and a laser light source which emits the laser light to the pentaprisms along the rotation axis is fixedly-provided on the foundation (for example, as shown in Japanese Patent Application Publication No. 2006-71545). In such a rotary laser emitting apparatus, each of the pentaprisms is rotated by the rotary body being rotated on the foundation, and the laser light emitted from the laser light source is emitted so as to pass through each of the rotary pentaprisms; therefore, the laser light is emitted while rotating. In such a rotary laser emitting apparatus, the occurrence of shake caused from an oscillation by the rotation or the like is controlled by a function of the pentaprisms, each of which deflects the entered light beam in a direction orthogonal to the entered direction and emits the deflected light beam, despite a change in attitude.
Incidentally, in such a rotary laser emitting apparatus, when another measurement device (such as a receiver for GPS or the like) is provided on top of the pentaprisms, that is, on top of the rotary body, the measurement device is properly rotated along with the rotary body. Therefore, a structure is proposed in which a fixed cylinder is provided around the rotary body; the rotary body is rotated in the fixed cylinder; and a position for mounting the other measurement device is provided on top of the fixed cylinder. However, in this case, a vertically continued part is necessary on the fixed cylinder. Here, however, it is preferable for the rotary laser emitting apparatus to be configured to emit the laser light over the whole circumference in the rotating direction of the rotary body in terms of heightening the accuracy of the measurement along with heightening the convenience of the measurement.
Therefore, instead of the structure in which such a fixed cylinder is provided, a structure may be proposed in which a supporting shaft portion extending along the rotation axis of the laser emitting section is provided on the foundation and also a through-hole through which the supporting shaft portion is led is provided on the rotary body; and the position for mounting the other measurement device is provided on top of the supporting shaft portion.
However, in such a structure as described above, it is necessary that the laser light emitting section be contained in the rotary body. Since the laser emitting section is contained in the rotary body rotating around the rotation axis, an attitude or an orientation of the rotary body is prone to shake in relation to an axis of the foundation (the rotation axis of the rotary body deviates from the axis of the foundation). Accordingly, the direction of emitted laser light is also prone to shake, and therefore, the accuracy of measurement degrades.